Are the conventional scoring systems efficient in predicting mortality of acute mesenteric ischemia?: Mortality estimation in patients with AMI

Acute mesenteric ischemia is a surgical emergency with high morbidity and mortality rates. Therefore, it is important to determine the prognosis for this disease. In the present study, we aimed to compare the prediction accuracy of 3 scoring systems: Acute physiology and chronic health evaluation II, sequential organ failure assessment score and simplified acute physiology score II (SAPS II). The retrospective cohort study was conducted in a university hospital. Eighty-two acute mesenteric ischemia patients were evaluated retrospectively. The mortality prediction abilities of the scoring systems were evaluated by comparing the prediction rates of > 10%, 30% and 50% and the actual mortality among survivors and non-survivors in pairs. Predicted mortality rates among survivors and non-survivors differed among the 3 classification systems. The mortality estimates of the SAPS II were closer to the actual mortality rates. Analysis of the estimated mortality rates as mortality risk limits showed that acute physiology and chronic health evaluation II was superior to sequential organ failure assessment score and SAPS II in estimating mortality rates, whereas SAPS II was more successful in detecting survivors. The estimated mortality rates of the 3 rating systems, the estimated mortality rates were higher in the non-survivor group than in the survivor group. The accuracy of the SAPS II in determining prognosis was relatively better.


Introduction
Acute mesenteric ischemia (AMI) is characterized by decreased tissue perfusion resulting in tissue hypoxia, depletion of cellular energy stores, and accumulation of toxic metabolites, which lead to cell death. Mortality from AMI is associated with the extent of ischemic necrosis of the gut, which results in sepsis and multi-organ failure. [1,2] Untreated or delayed in treatment results in a mortality rate of over 95% while surgical treatment decreases the mortality rate to approximately 70%. [3] As the duration of symptoms prolongs, mortality increases from 12% to 98% after 48 hours. [4] For this reason, early diagnosis and revealing the severity of AMI is essential.
Scoring systems put forth mortality risks in patients in intensive care units, which leads to better management of healthcare expenses. The worst physiological parameters within the first 24 hours of hospitalization were used for calculations of the acute physiology and chronic health evaluation II (APACHE II) and simplified acute physiology score II (SAPS II) scores, 2 of the most commonly used scoring systems. [5,6] The sequential organ failure assessment (SOFA) aims to predict mortality according to organ failure.
Only a few studies have used the conventional scoring systems for AMI, and none have compared these scoring systems.

Objective
The objective of this study was to compare the predictive ability of APACHE II, SOFA, and SAPS II for mortality from AMI. [7][8][9] Yilmaz et al. • Medicine (2022) 101:52 Medicine

Methods
The study protocol was approved by the local ethical committee (IRB:2021-09-22). The medical records of 82 patients with AMI between January 2010 and January 2021 were retrospectively analyzed. A diagnosis of the intestinal ischemia was confirmed both surgically and pathologically.
The scores of APACHE II, SOFA, and SAPS II scores were calculated using the calculation tools via the links below, respectively: https://clincalc.com/Icu-Mortality/APACHEII.aspx, https://clincalc.com/IcuMortality/SOFA.aspx, https://clin-calc. com/IcuMortality/SAPSII.aspx. The worst clinical findings and laboratory values within the first 24 hours in the intensive care unit were used for the calculation.

Statistical analysis
SPSS version 25 software (SPSS Inc., Chicago, Illinois) was used for statistical analysis. Because the data values were within wide ranges, and the SOFA scoring system presents the predicted mortality rates in ranges, it was necessary to categorize the patients into 4 groups according to their predicted mortality rates as follows: group 1, < 10%; group 2, between 10% and 29%; group 3, between 30% and 49%; and group 4, ≥ 50%.
First, we assessed the predictivity of the 3 scoring systems for mortality by comparing estimated mortality rates across mortality groups (survivors/nonsurvivors) using the chi-square test. We then compared actual mortality in mortality groups with estimated mortality rates of > 10%, 30% and 50% for each scoring system system.

Results
The demographic data of patients, actual death rates, estimated mortality rates, and length of hospital stay are presented in Table 1. We confirmed the ability of the 3 scoring systems to predict death by showing that the estimated mortality rates differed between the surviving and non-surviving groups. The actual mortality rates in the estimated mortality groups are shown in Table 2, where the SOFA and SAPS II scoring systems were better able to estimate the actual mortality rates. In addition to predictive accuracy, we assessed the proportion of patients who died with > 10%, 30%, and 50% of the predicted mortality rates, and the proportion of patients who survived with mortality rates of < 10%, 30%, and 50% (Table 3 and  Table 4, respectively). The mortality and survival predictions of the scoring systems were statistically compared in pairs (Table 5 and Table 6). Accordingly, it was observed that SOFA and SAPS II predicted higher mortality higher, and SAPS II was more successful in predicting survival.

Discussion
The mortality rates of AMI are high if not treated early. When mesenteric blood flow is impaired, the intestines continue to be remain viable in the first 12 hours. However, if this period was between 12 to 24 hours, the preservation of intestinal viability decreased to 56%, and if it lasted longer than 24 hours, it decreased to approximately 18%. Therefore, early diagnosis and initiation of treatment as soon as possible will decrease the mortality rate. [10,11] Most of the laboratory parameters for this purpose alone are not sufficient to determine the outcome in the early stage of AMI but are more useful in late-stage disease. [12] For this reason, we evaluated the efficiency of the scoring systems to predict the prognosis of the disease in the early period.
In the present study, the mortality rate of patients with AMI was 46.3%, lower than that reported in the literature. [13] We believe that the most important reason for this is that treatment could be started without delay after early diagnosis. The medical records revealed that the frequency of comorbid diseases, of which diabetes (62.2%) and hypertension (50%) were the most Table 1 Estimated mortality rates calculated according to demographic data, length of stay, actual mortality rates and scoring systems of patients with AMI. common, was higher than in previous studies. [14,15] Regardless of the etiology, advanced age is an eminent risk factor for AMI. [16] The mean age of the patients in our study was 69. Similarly, Hsu et al reported that the mean age of patients with mesenteric ischemia was 70 years. [17] The median hospital stay of all patients and surviving patients was 9 days and 11 days, respectively. Caluwaerts et al [18] reported a greater difference in the length of hospital stay between all patients and survivors. In their study, the average hospital stay of all patients with mesenteric ischemia was 13 days, while in the surviving patients, it was 33 days. [18] We consider that this difference was due to the ratio of survivors to all patients. Healthcare providers use mortality prediction models to manage resources and evaluate the quality of care and therapeutic interventions. In our study, we compared the APACHE II, SOFA, and SAPS II scoring systems, which are the most commonly used in our center.
In the present study, we found that the scores of the rating systems were higher in the non-survivor groups than in the surviving group, as shown in previous studies. [7,8] The median APACHE II scores in both survival groups were higher than those reported by Wu et al [7] (13 vs 11.9; 21.5 vs 14.3, respectively). On the other hand, the median SAPS II scores were lower than those reported by Piton et al [8] have reported in the NUTRIREA2 trial (39 vs 59). [8] Viswanathan et al [19] have reported higher SOFA scores both in survivors and non-survivors compared to our study (3 vs 8.82; 8 vs 12.86, respectively). [19] Even though the scores of all 3 systems were different in the survival groups, the predicted mortality rates using the SAPS II were more accurate than those using the APACHE II and SOFA scoring systems. Among patients with predicted mortality < 10%, SAPS II was the scoring system closer to the predicted mortality, whereas APACHE II and SOFA overestimated mortality. Within the 10% to 29% and 30% to 49% prediction widths, mortality estimates from all scoring systems were higher than the actual mortality rates. However, it was remarkable that the APACHE II scoring system underestimated mortality among patients with predicted mortality rates of > 50%.
When we analyzed the estimated mortality rates as mortality risk limits, we observed that even though APACHE II was superior to SOFA and SAPS II in estimating mortality among highrisk patients, APACHE II underestimated the mortality. Among the survivors, the SAPS II was the best system for predicting the survival rates.
Variations in the treatment strategies might have affected our results. In addition, while the SOFA scoring system aims more to detect organ dysfunction and morbidity, APACHE II and SAPS II are designed to detect mortality. [20] Validation of our results in larger studies is requisite.
With these scoring systems, the subjective prognostic estimations and severity assessments can become more objective.

Conclusions
As a result, although all 3 scoring systems were predictive of the prognosis of AMI, they were far from perfect. The accuracy of SAPS II in determining prognosis was relatively better.